Grinding machines have been used for well over a hundred years to grind various types of beans, grains, rice and other materials. In modern times, the unprecedented popularity of high quality fresh coffee, for example, has resulted in a sales explosion of grinding machines for use both in commercial and home settings.
The optimal preparation of coffee is dependent on bean quality, roast execution, grind consistency, product freshness, and equipment cleanliness. After harvest and drying, whole coffee beans are roasted. Roasting serves to draw out the beans' essential oils in preparation for the brewing process. After roasting, and just prior to brewing, the beans are ground. Grinding increases the coffee bean surface area available for the extraction of coffee oils during brewing.
It is generally agreed that the optimal taste profile of coffee is achieved when the time between grinding and brewing is the shortest possible. It is also accepted that the taste of the highest quality coffee beans can easily be contaminated. The most common cause of contamination is the co-mingling of fresh beans with rancid coffee oil and particulate residue left behind from previous preparations.
In an effort to minimize the time between grinding and brewing coffee, there are coffee bean grinders in place in the vast majority of supermarkets, grocery stores, restaurants, and coffee retailers around the world. Many households also own grinding appliances to further reduce the time between grinding and brewing.
The coffee industry follows a rigorous procedure of cleaning coffee brewing equipment to insure the removal of coffee oil residue from servers, faucets, urns, decanters, filter baskets, screens, porta-filters, and even whole bean containers. These cleaning procedures are based on an effort to reduce the chance of contamination of fresh beans or brewed coffee with rancid oil residue and old bean particles. Procedures and products exist for cleaning brewing equipment of all varieties. However, there is no standard method, procedure, or product for easily removing coffee oil residue or particles from grinding equipment without time consuming disassembly of the grinding equipment and manual wiping and brushing of the grinder discs and other parts
Since grinding is the first step in the brewing procedure, it is also the first opportunity for accumulated coffee oil residue (which has possibly turned rancid) to contaminate freshly ground beans. Each time a bean is ground, there is an opportunity for it to contact the grinder burrs or blades. These components may often be coated with coffee residue such as oil and very fine coffee particulate.
Aside from the possible contamination of freshly ground beans by the oily residue of previously ground beans, there is also a grinder cleaning issue surrounding “flavored coffees.” Flavored coffees are roasted coffee beans that have been commercially infused with essential oils and flavorings. This is done to enhance their taste and aroma. Some popular flavored coffees include hazelnut, amaretto, vanilla, and blueberry.
The brewing preparation methods for flavored coffee are identical to those of non-flavored coffees. This includes the need to grind the beans before extraction of essential oils from the coffee—both natural and added oils. While it has already been established that the oils of natural coffee beans accumulate in grinders, it should be noted that the added oils of flavored coffees also may accumulate in grinders.
One issue that arises with the accumulation of flavorings in grinders is co-mingling. This occurs when residue from one flavor variety is ground after another in the same grinder or when natural coffee is ground in the same grinder as flavored coffee. For this reason, most retailers dedicate one grinder for all flavored coffees and a second for non-flavored coffees. Although this removes the chance of flavoring un-flavored beans, it does not eliminate cross contamination of two or more different flavor types. Furthermore, there is also the chance of an accidental use of flavored coffee in the grinder dedicated for regular roasts. When this occurs, the dedicated “non-flavor” grinder must be disassembled and cleaned to remove the flavoring residue. This is a costly procedure, often requiring a service technician's visit.
In addition to the problems of cross-contaminated flavorings, the added oils in flavored coffee have a tendency to “gum up” grinder burrs and blades. The flavoring additives create a sticky substrate that can affect grinder effectiveness. Unfortunately, regardless of the possibly substantial mechanical effect of oily accumulation on grinders, the accumulated oils are certain to infuse and contaminate all subsequent batches of coffee.
It should also be noted that there are issues of contamination related to decaffeinated coffee being ground in a machine regularly used for caffeinated coffee. If a grinder is not properly cleaned between different types of coffees, there is a chance for contamination. In some people, there is a health risk related to drinking caffeinated coffee and even the slightest residue could cause a problem.
At present, there are only two known techniques for purging oil and particle accumulation in coffee grinding equipment. Due to the fact that most commercial and home grinding burrs are made of either steel or ceramic and held in tight spaces near electrical motors, water or other liquids cannot be introduced into the grinding chamber. Adding liquid could either rust the steel burrs or damage electrical circuitry. As a result, both presently known procedures have major challenges.
Most grinder manufacturers and sellers recommend periodic disassembly of grinders and brushing of burr teeth and wheels with a soft bristle. While effective at removing particle residue, this technique is both time consuming and complicated. In addition, the process of brushing does nothing to absorb or remove oil residue.
A second, much less frequently discussed, grinder cleaning technique is the delivery of common uncooked rice into the grinding chamber. Although this technique provides the possibility of a quick and easy approach to trying to purge the burrs of coffee residue, the starchy nature of rice, the inaccurate portioning guidelines, and the gummy residue of rice do not provide a reliable solution.